The purification of 3,3-dimethylallyl- and geranyl-transferase and of isopentenyl pyrophosphate isomerase from pig liver

Abstract

The enzyme catalysing the synthesis of farnesyl pyrophosphate from dimethylallyl pyrophosphate and isopentenyl pyrophosphate, or from geranyl pyrophosphate and isopentenyl pyro-phosphate, has been purified 100-fold from homogenates of pig liver. The enzyme has optimum pH 7.9 and requires Mg2+ as activator in preference to Mn2+; it is inhibited by iodoacetamide, N-ethylmaleimide, p-hydroxymercuribenzoate and phosphate ions in addition to the products of the reaction, inorganic pyrophosphate and farnesyl pyro-phosphate. From product-inhibition studies of the geranyltransferase reaction, the order of addition of sybstrates to and release of products from the enzyme has been deduced: gernayl pyrophosphate combines with the enzyme first, followed by isopentenyl pyrophosphate. Farnesyl pyrophosphate dissociates from the enzyme before inorganic pyro-phosphate. The existence of isopentenyl pyrophosphate isomerase in liver is confirmed. Methods for the preparation of the pyrophosphate esters of isopentenol, 3,3-dimethylallyl alcohol, geraniol and farnesol are also described.